The term “biomass energy” is used herein to refer to energy obtain from solid biofuels such as wood, sawdust, wood chips, grass cuttings, domestic refused, charcoal, agricultural waste, energy crops, and dried manure. To release biomass energy, solid biofuels are typically burned in a fireplace, stove, or furnace to create heat. Certain solid biofuels, such as wood (e.g., firewood) can be burned directly; other solid biofuels, such as sawdust and wood chips, may be processed into pellets, cubes, pucks, or the like to facilitate burning. The heat generated by burning solid biofuels may be used directly or may be transferred to another medium to facilitate distribution of the heat throughout a dwelling.
In general, the market for biomass reduction systems may be divided into commercial furnaces and residential stoves, fireplaces, and furnaces. The present invention is of particular significance in the context of furnaces designed for use in a residential setting. Commercial furnaces are typically relatively large, and the biofuels used in a commercial furnace typically have a predetermined form factor and composition. For example, commercial furnaces are designed to use densified pellets to facilitate handling of the biofuels and to allow the furnace to be designed for a biofuel having a known energy density. Commercial devices are further typically designed to run continuously and at high utilization or demand and do not operate efficiently at low utilization or demand.
In contrast, in residential or domestic settings, biofuels are commonly burned in a stove or fireplace, and the generated heat is transferred as radiant heat energy to the surrounding environment. Residential stoves and fireplaces are typically relatively inefficient, resulting in incomplete burning of the biofuel and thus the discharge of soot, ash, and gasses through the smokestack or chimney.
Additionally, in North America, biofuels burned in a residential setting most commonly take the form of firewood. Firewood is typically obtained from trees of different species and comes in different shapes, sizes, and moisture content; the form factor and composition of firewood is thus typically not known in advance.
The need exists for biomass reduction furnaces designed for residential settings that do not require biofuels having a known form factor and composition, that transfer heat energy to water for use in domestic purposes (e.g., heating domestic hot water or radiant heating systems), and that result in complete burning of the biofuel.